Method of manufacturing a pressure seal type piezoelectric oscillator

ABSTRACT

The invention relates to a piezoelectric oscillator wherein a case and a stem are coated with a solder containing 90% and higher of lead, an inner lead is also coated with the solder thereby fixing a piece of piezoelectric oscillator by melting the solder. The invention further relates to a piezoelectric oscillator wherein the piezoelectric oscillator is performed casing by resin or metallic plate, and to a piezoelectric oscillating apparatus wherein IC and a piezoelectric oscillator are internally mold to achieve a molding of high efficiency without inferiority while surface mounting.

This is a continuation of application Ser. No. 07/563,879, filed Aug. 6,1990, which is a continuation of Application Ser. No. 07/265,865, filedon Oct. 6, 1988 now abandoned.

TECHNICAL FIELD

The present invention relates to a pressure seal type piezoelectircoscillator wherein a piece of quartz oscillator is sealed in case by useof a press-fitting system of case, a resin mold type piezoelectricoscillator wherein the pressure seal type piezoelectric oscillator ispackaged by resin, a case-inserted type piezoelectric oscillator havinga separate case with the pressure seal type piezoelectric oscillatorinserted therein and a piezoelectric oscillating apparatus wherein thepressure seal type piezoelectric oscillator and an IC having oscillatingcircuit are sealed by resin.

TECHNICAL BACKGROUND

A conventional piezoelectric oscillator have been employed a fasteningmethod by adhesive agent 101 or a fastening method by solder having theratio of Sn to Pb, 6:4 or 9:1, for fastening a piece of piezoelectricoscillator. Further, pressure seal method in which the case is coatedwith solder 102 or gold by plating, welding method and cold pressurewelding method are employed for sealing.

Furthermore, a conventional resin mold piezoelectric oscillator isconstructed as depicted in FIG.16. This piezoelectric oscillator is aintegrally formed oscillator in which a piece of piezoelectircoscillator 103 is adhered to inner lead 105 of stem 104 by an adhesiveagent such as polyimide series one, stem 104 and case 106 are sealed bygold as shielding material 107 and the pressure seal type piezoelectricoscillator and the lead frame are adhered by welding.

A conventional piezoelectric oscillator have been constructed asdepicted in FIG.17, wherein the above-described pressure seal typepiezoelectric oscillator 109, semiconductor 110 which electicallyoscillates pressure seal type piezoelectric oscillator 109 and the leadframe which electrically connects pressure seal type piezoelectricoscillator 109 with semiconductor 110 have been molded by resin 111.

However, when the above-described prior art is employed as SMT (SurfaceMount Technology) parts, the temperature of the whole parts rises up to220°-260° C. when they are packaged on the substrate and the soldercontaining 40% and less of lead are melted. In addition to thisfundamental disadvantage, deterioration of the properties, shift infrequency and in equivalent resistance value of pressure seal typepiezoelectric oscillator by gas containing organic components ejectedfrom the soldering are caused.

It is, therefore, an object of the invention to solve theabove-described disadvantages and to provide an improved pressure sealtype piezoelectric oscillator, resin mold type piezoelectirc oscillatorand piezoelectric oscillating apparatus, each having heat resistanceapplicable for SMT packaging at 260° C. and higher and having propertiesexcellent in high temperature frequency aging.

DESCRIPTION OF THE INVENTION

The present invention is directed to a pressure seal type piezoelectircoscillator wherein a case and a stem are coated with solder containing90% and higher of lead therein, a piece of piezoelectric oscillator isadhered by melting the solder coated on an inner lead of the stem andthe case and the stem are hermetically sealed by press-fitting methodwith the solder as a shielding material.

The present invention is directed to a resin mold type piezoelectricoscillator, wherein the case and the stem are coated with soldercontaining 90% and higher of lead, a piece of piezoelectric oscillatoris adhered by melting the solder coated on the inner lead of the stemand an outer lead and a lead frame of the pressure seal typepiezoelectric oscillator wherein the case and the stem are hermeticallysealed by pressure seal method with the solder as a shielding materialare adhered to each other, and such pressure seal type piezoelectricoscillator and the lead frame are integrally molded by resin.

Further, according to the present invention, the case and the stem arecoated with solder containing 90% and higher of lead, a piece ofpiezoelectric oscillator is adhered by melting the solder coated on theinner lead of the stem and the stem are hermetically sealed bypress-fitting method with the solder as a shielding material.

The present invention is directed to a case-inserted type piezoelectricoscillator having a rectangular case having a thickness within the rangefrom 0.05 to 1.5 mm and whose coross section has one or more corners atthe periphery of cylindrical pressure seal type piezoelectric oscillatorexcepting the lead portion.

Furthermore, the present invention is directed to a pressure seal typepiezoelectric oscillating apparatus wherein the case and the stem arecoated with the solder containing 90% and higher of lead, a piece ofpiezoelectric oscillator is adhered by melting the solder coated on theinner lead of the stem, and further a pressure seal type piezoelectricoscillator wherein the case and the stem are hermetically sealed bypress-fitting method with the solder as a shielding material, asemiconductor (IC) for electrically oscillating the pressure seal typepiezoelectric oscillator and the lead frame are molded by resin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural view of a pressure seal type piezoelectricoscillator constructed in accordance with the invention.

FIG. 2 is a graph showing condition of a solder.

FIG. 3 is a structural view of a pressure seal type piezoelectricoscillator constructed in accordance with an alternate embodiment of theinvention.

FIG. 4 is a structural view of the pressure seal type piezoelectricoscillator constructed in accordance with another embodiment of theinvention.

FIG. 5 is a structural view of a resin mold type piezoelectricoscillator constructed in accordance with another embodiment of theinvention.

FIG. 6 is a perspective view of a resin mold type piezoelectricoscillator of the invention.

FIG. 7 is a structural view of a resin mold type piezoelectricoscillator constructed in accordance with an application embodiment ofthe invention.

FIG. 8 is a perspective view of a resin mold type piezoelectricoscillator constructed in accordance with an application embodiment ofthe invention.

FIG. 9 is a perspective view of a resin mold type piezoelectricoscillator constructed in accordance with another embodiment of theinvention.

FIG. 10 is a structural view of a case-inserted type piezoelectricoscillator of the invention.

FIG. 11(a) is a cross-sectional view of a case-inserted typepiezoelectric oscillator of the invention.

FIG. 11(b) is a cross-sectional view of a case-inserted typepiezoelectric oscillator constructed in accordance with anotherembodiment of the invention.

FIG. 11(c) is a cross-sectional view of a case-inserted typepiezoelectric oscillator constructed in accordance with anotherembodiment of the invention.

FIG. 12 is a perspective view of a piezoelectric oscillator in use of apressure seal type piezoelectric oscillator of the invention.

FIG. 13(a) is a cross-sectional view of a piezoelectric oscillator inuse of a pressure seal type piezoelectric oscillator of the invention.

FIG. 13(b) is a main plan view showing a piezoelectric oscillatorconstructed in use of a pressure seal type piezoelectric oscillator ofthe invention.

FIG. 14(a) is a main plan view of a piezoelectric oscillator constructedin accordance with the invention.

FIG. 14(b) is a main cross-sectional view of a piezoelectric oscillatorof the invention.

FIG. 15 is a cross-sectional view of a conventional presssure seal typepiezoelectric oscillator.

FIG. 16 is a structural view of a conventional resin mold typepiezoelectric oscillator.

FIG. 17 is a main cross-sectional view of a conventional piezoelectricoscillator.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a structural view of a quartz oscillator as an embodimentof a pressure seal type piezoelectric oscillator of the presentinvention. A tuning fork-shaped piece of quartz oscillator 1 which ismade of quartz plate by photolithography is adhered to lead 3 of stem 2wherein lead 3 is sealed to metallic ring 7 with glass, byhigh-temperature solder 4 provided thereon by plating having meltingpoint of 260° C. and higher and the ratio Sn to Pb about 1:9 as shown inFIG. 2, a graph showing conditions of solder. Further, a quartzoscillator is completed when case 6 coated with high-temperature solder5 is hermetically sealed by press-fitting method. Since Sn is cracked orbroken at very low temperature at times, the solder with a large amountof Pb has good heat resistance and is stable at very low temperature.High heat resistance and operation efficiency are required for thesolder so that a high-temperature solder containing not only Sn and Pbbut also with a third metal such as Ag can be applicable. Generally, arotating type plating method is employed for plating the pressure sealtype stem and case with the solder so that the solder is adhered toentire metallic portion of stem 2 and case 6. Then, the organiccomponents in the condition of gas are ejected from the plating,resulting in a deterioration in properties, such as an adhesion of thegas to a piece of oscillator or lowering the degree of vacuum. Thedeterioration in properties is also caused when not entire metallicportion but only the inner periphery of case 6 is plated with the solderas shown in FIG. 3. Therefore, partial plating, such as thathigh-temperature solder 4 is used at the fastening portion of quartzoscillator piece 1 with lead 3 and high-temperature solder 5 at thesealing portion of stem 2 with case 6 is more desirable. If quartzoscillator piece 1 is hermetically sealed at high temperature (roomtemperature to 260° C.) in case that the entire metallic portion of thecase and of the stem are plated with the solder, the equivalentresistance value is extremely increased (100% and higher, on ocasion)and aging in frequency is caused considerably, which sometimes stopsoscillating. Accordingly, before and/or while stem 2 is hermeticallypress-sealed into case 6, the gas should be ejected outward by heatbaking. Desirable temperature for such baking is indicated in FIG. 2 asthe temperature within the portion marked with slant lines surrounded byeutectic curve ab, liquidus curve ac and a line indicating 90% of leadcontent. Organic components can be ejected thoroughly by heat baking inthis condition, thereby limiting the increase in the equivalentresistance value within several %.

Further, when press-fitting method is applied, the high-temperaturesolder is plated at least on the side of the case of sealing portion sothat airtightness can be maintained. The metallic ring of the stem canalso be plated with Ni or Cu.

The above-described structure can be achieved with the manufacturingtechnique similar to the conventional one while being inexpensive tomanufacture with low cost materials, which achieves mass production andminiature in size. Becuase, large burden in the process in which quartzoscillator piece is adhered can be lightened by applying the soldermelting method, which results in an easier production. Further, theproduction also becomes easier with low cost materials by applying thepress-fitting method as sealing method.

As the conventional quartz oscillator has low heat-resistance property,the mounting method similar to one applied for the SMT which has takenrapid strides in these days has not been applied. However, the pressureseal type quartz oscillator of the present invention can be mountedsimultaneously with the SMT parts. The quartz oscillator can beconfirmed that no deterioration of properties thereof is caused at 260°C. of the mounting temperature and at 150° C. of preservationtemperature.

This embodiment is described employing a tuning fork-shaped quartzoscillator piece, and other piezoelectric oscillator piece havingdifferent configuration and material such as a rectangular AT cut quartzoscillator piece or tantalic acid lithium oscillator piece are confirmedthat no deterioration of heat-resistance property is caused.

The resin mold type piezoelectric oscillator is adhered to lead fram 10by a method such as that the solder of outer lead 9 of pressure sealtype piezoelectric oscillator 8 is melted, as shown in FIG. 5. Thewelding is more sufficient for solid adhesion. The resin mold typepressure seal piezoelectric oscillator can be completed by integralmolding of these members with epoxy or phenol series resin 11. FIG. 6 isa perspective view showing a structure wherein the lead frame is broughtout to the end portion. In this structure, the lead frame is bent insidetoward the base, which is called as J-bend, but the lead frame can bebent outside, which is called as gullwing. Further, the lead frame canbe brought out to the side face as shown in FIG. 7. FIG. 8 is aperspective view thereof. It is better to perform marking, such as toround off the corners of the periphery of resin, in order to distinguishthe lead which is to be conducted for operating the piezoelectricoscillator from other leads.

FIG. 9 is a perspective view of a resin mold type piezoelectricoscillator constructed in accordance with an alternate embodiment of theinvention. The above-described embodiment relates to the structure ofsurface mounting type, but the lead-inserted type is also applicable.

According to a case-inserted type piezoelectric oscillator, rectangularcase 36 is attached to the periphery of the above-described pressureseal type piezoelectric oscillator and lead 34 is bent, as shown in FIG.10. Rectangular case 36, if it is made of metal, has a thickness withinthe range from 0.05 to 1.5 mm, whereby it can be molded by a method suchas press easily. Further, rectangular case 36 can also be made of resin.It is fixed by welding, adhesive agent or fitting. The configuration ofthe rectangular case can be a polygon having three or eight faces aswell as one having four faces, as shown in FIG. 11. The rectangular casemade of metal can also be applied as an earth.

Next, according to the first embodiment of a piezoelectric oscillator inuse of the pressure seal type piezoelectric oscillator of the inventionas shown in FIGS. 12 and 13, pressure seal type piezoelectric oscillator12 and semiconductor 13 for electrically oscillates oscillator 12 arearranged on the same plane, and they are electrically connected to forma oscillation circuit, by melting the wire bonding of metallic fine wire15 and the solder of outer lead 16 of pressure seal type piezoelectricoscillator 12 through lead frame 14. The piezoelectric oscillatorfurther comprises resin 17 including pressure seal type piezoelectricoscillator 12, semiconducntor 13, lead frame 14 and metallic fine wire15. Since lead frame 14 is not rigid enough and the wire can be cut downon ocasion when pressure seal type piezoelectric oscillator 12 isadhered thereto, it is to be desired that lead 41 is arranged on theopposite side to the location of semiconductor 13 and near outer frame42 of the lead frame.

The second embodiment of the piezoelectric oscillator is describedreferring to FIGS. 14(a) and 14(b), in which pressure seal typepiezoelectric oscillator 18 and semiconductor 19 which electricallyoscillates oscillator 18 are disposed on the upper surface and the lowersurface of lead frame 20 respectively and tab 21 of lead frame 20 towhich semiconductor 19 is adhered is pushed out toward the side ofpiezoelectric oscillator 18 to make a parallel contact with pressureseal type piezoelectric oscillator 18, thereby maintaining a clearancefor electric insulation between pressure seal type piezoelectricoscillator 18 and lead frame 20. This prevents not only the electricconduction between piezoelectric oscillator 18 and a plurality of leadframe 20 but also short circuit between lead frames 20. According tothis structure, the area is a half of that of the case wherein pressureseal type piezoelectric oscillator and the semiconductor are arranged onthe plane and the thickness is a sum of the minimum thicknesses of eachpart.

In the end, the entire body is mold by heat resistant resin 22 includingpiezoelectric oscillator 18, semiconductor 19 and lead frames 20 and 21.

According to the piezoelectric oscillator described in the aboveembodiment, the portion to which the piece of oscillator is attached bythe solder, the bonding portion between the case and the stem and thatbetween the lead of pressure seal type piezoelectric oscillator and thelead frame are so constructed to have 260° C. and higher heatresistance, including the other parts.

The configuration of the entire body is the form of lead frame, which iscalled gullwing, for flat package corresponding to SMT as shown in FIG.12. It can be applied to a form of lead-inserted as an insertion partsuch as DIP(dusl in-line package) type.

It can further be applied to a form of J-bend lead frame for flatpackage as an embodiment.

According to the piezoelectric oscillator described in the aboveembodiment, the case and the stem are coated with the solder containing90% and higher of lead, the piece of piezoelectric oscillator is adheredby melting the solder coated on the inner lead of the stem and the caseand the stem are hermetically sealed with the solder as a shieldingmaterial by the pressure seal method. Therefore, the piezoelectricoscillator can be adhered directly by the solder coated on the leadwithout using adhesive agent and the case and the stem can be pressuresealed directly by the solder coated thereon, which renders a pressureseal type piezoelectric oscillator having sufficient heat resistancebeing inexpensive for materials thereof and production. Further, sincethe case and the stem to which the piece of piezoelectric oscillator isadhered by melting the solder are hermetically sealed by the pressureseal method at the temperature wherein the solder is melted, thepiezoelectric oscillator having low equivalent resistance value,improved temperature ageing properties and reliability can be obtained.

Further, according to the resin mold type piezoelectric oscillator ofthe present invention, the case and the stem are coated with the soldercontaining 90% and higher of lead, the piece of piezoelectric oscillatoris adhered by melting the solder coated on the innner lead of the stem,and the case and the stem are hermetically sealed with the solder as ashileding material by the press-fitting method. Furthermore, the outerlead of such pressure seal type piezoelectric oscillator is adhered tothe lead frame and the pressure seal type piezoelectric oscillator andthe lead frame are integrally mold by resin. Hence, an inexpensivepiezoelectric oscillator having high quality and sufficient heatresistance, which is further convenient to operate for automaticmounting and the like, can be obtained.

Furhtermore, according to the case-inserted type piezoelectricoscillator of the present invention, the case and the stem are coatedwith the solder containing 90% and higher of lead, the piece ofpiezoelectric oscillator is fixed by melting the solder coated on theinner lead of the stem, a rectangular case having a thickness within therange from 0.05 to 1.5 mm and whose periphery in the cross section hasone or more corners excepting the lead portion of the pressure seal typepiezoelectric oscillator wherein the case and the stem are hermeticallysealed with the solder as a shielding material by the pressure sealmethod is attached. Therefore, an inexpensive piezoelectric oscillatorhaving high quality and sufficient heat resistance, which is furtherconvenient to operate for automatic mounting and the like, can beobtained.

According to the the piezoelectric oscillating apparatus of the presentinvention, the case and the stem are coated with the solder containing90% and higher of lead and the solder is used as a mounting material ofthe piece of oscillator and a hermetically shielding material, and thelead of the piezoelectric oscillator is weld as a composition metallayer wherein metallic lead of the lead frame contains 90% and higher oflead, thereby achieving piezoelectric oscillating apparatus having 260°C. and higher heat resistance.

In addition, the pressure seal type piezoelectric oscillator and thesemiconductor are disposed on either side of the lead frame respectivelyand they are insulated by pushing out the tab of the lead frame, therebyproviding a small-sized piezoelectric oscillator having good heatresistance can be provided.

What is claimed is:
 1. A method of manufacturing a pressure seal typepiezoelectric oscillator, comprising:(a) coating a high-temperaturesolder on at least a portion of an oscillator case having an opening, oron a stem for sealing the case opening, the solder comprising at leastabout 90% Pb; (b) coating the solder on at least a part of an inner leadwhich passes through the stem; (c) positioning a portion of a quartzcrystal oscillator on the solder coated in step (b) such that the quartzcrystal oscillator and the inner lead are adhered to each other; (d)heat baking the solder from step (a) while the solder is in a semi-fluidcondition to remove dissolved gas; and (e) press-combining the case andthe stem to convert the solder between the case and stem into a sealingmaterial.
 2. The method of claim 1, wherein steps (d) and (e) arecarried out simultaneously.
 3. The method of claim 1, wherein the solderbetween the case and stem hermetically seals the case and the stem. 4.The method of claim 1, wherein the solder includes Sn.
 5. The method ofclaim 4, wherein the solder includes Ag.
 6. A method of manufacturing apressure seal type piezoelectric oscillator, comprising:(a) coating ahigh-temperature solder consisting essentially of Sn, Ag and at least90% Pb, on at least a portion of an oscillator case having an opening,or on a stem for sealing the case opening; (b) coating the solder on atleast a part of an inner lead which passes through the stem; (c)positioning a portion of a quartz crystal oscillator on the soldercoated in step (b) such that the quartz crystal oscillator and the innerlead are adhered to each other; (d) heat baking the solder from step (a)while the solder is in a semi-fluid condition to remove dissolved gas;and (e) press-combining the case and the stem to convert the solderbetween the case and stem into a sealing material.
 7. The method ofclaim 6 wherein the solder consists essentially of Pb and Sn.